AN ABSTRACT OF TIlE THESIS OF Russell David Earnest for the M. S. (Name of student) (Degree) in Fisheries presented on February 22,1967 (Major) (Date) Title. Production of the Snail Oxytrema silicula (Gould) in an ExDerimental Stream Abstract approved Redacted for Privacy Gerald F. Davis A study was performed of the influence of enrichment on the production and food relations of the stream snail, Oxytrema silicula, in the Berry Creek experimental stream from October, 1963 through February, 1965.Four experimental stream sections that were separated from each other by screens were used in thetudy.Two upstream sections (I and II) were not enriched; receiving energy only from sunlight and natural allochthonous materials.Two down- stream sections (III and TV) w're continuously enriched with sucrose and urea. As aresult,growthsof the bacterium Sphaerotilus natans developed on therifflesof thesesections.The removal of trees from alongside Sections II and IV resulted in smaller quantities of leaves and more sunlight reaching these sections than reached Sec- tions I and III. Snails were removed monthly froma0. 26m2area of riffle of each section and were separated into different size-groups.The groups were considered to represent the 1959, 1960, 1961, 1962, 1963, and 1964 year-classes.Production for each age-class was calculated from measurements of growth rate and average biomass. Aquarium experiments with snails of sizes similar to those of the 1961 year-class, which were the most abundant in the stream, established relationships between rates of growth and foodconsump- tion during two seasonal periods.Estimates of annual total food consumption in each section were based upon these relationships and upon knowledge of the growth rates of 1961 year-class snails and of the total snail biomass of all age-classes. Laboratory stream experiments were performed which estab- lished that snails were able to utilize Sphaerotilus for growth.Re- sults of studies in which snails, along with different types of leaves, wcre suspended in packets in an unenriched and in an enriched section of the stream showed that the most abundant leaves, alder and maple, were utilized by snails but that oak leaves were not.Comparison of rates of decomposition of leaves suspended alone in packets in the stream indicated that decomposition was greater in enriched than in unenriched sections. Snail production was found to be approximately seven-fold greater in enriched than in unenriched sections.Most of the pro- duction in enriched sections was by the 1960 year-class of snails. Production was greatest in unenriched sections byyounger age-groups than in enriched sections.Food consumption, like pro- duction, was estimated to be approximately seven-fold greater in enriched than in unenriched sections Some relationships between snail production and the energy resources of the different sections are discussed. Production of the Snail Oxytrema silicula (Gould) in an Experimental Stream by Russell David Earnest A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science June 1967 APPROVED: Redacted for Privacy Assistant Professor of Fisheries in charge of major Redacted for Privacy Head of Department of Fisheries and Wildlife Redacted for Privacy Dean of GraduateSchool February 22,1967 or Russell David Earnest A c kn ow 1 e d g m en t s I am indebted to Dr. Gerald F. Davis, Assistant Professor of Fisheries, and Dr. Charles E. Warren, Professor of Fisheries, for their counsel and guidance during all phases of this study.Thanks are also due the various members of the Berry Creek staff who aided in the collection of the bottomsamples. I am grateful to Dr. John R. Donaldson for reviewing the thesis and offering many constructive criticisms. Special thanks must go to my wife Corinne for her help and patience during the course of the study. The financial support of this study was through the Water Pollution Training Grant No. SP1WP52, U. S. Public Health Service. TABLE OF CONTENTS Page INTRODUCTION................................ 1 METHODS AND MATERIALS........................ 5 Experimental Facilities....................... 5 Sampling Procedures 9 Size Grouping and Measurement of Snails 11 Estimation of Biomass, Growth Rate, and Production 12 Estimation of Food Consumption 14 Utilization of Sphaerotilus by Snails 16 Utilization of Leaves by Snails...................1 7 Caloric Conversion..........................1 7 RESULTS AND INTERPRETATION .................... 19 Growth Rates..............................19 Biomass 24 Production 31 Food Consumption...........................34 Utilization of Sphaerotilus by Snails 38 Utilization of Leaves by Snails 38 DISCUSSION...................................42 BIBLIOGRAPHY................................50 LIST OF FIGURES Figure Page 1. Diagram of Berry Creek Experimental Stream 6 showing research facilities. 2. Stream flow and maximum and minimum stream 8 temperature in the controlled section of Berry Creek. 3. Curves relating values of mean snail weight, in 20 milligrams, to sampling dates.Values taken from the curves were used to compute mo:rithly growth rates for each year-class of snails in each experi- mental section. 4. Weight-frequency of all snails in biomass sample 21 taken from Section III during August, 1964. 5. Weight-frequency of all snails in biomass sample 22 taken from Section III during November, 1964. 6. Relationship between rates of food consumption and 35 growth of snails held in aquaria and fed different rations of known caloric value.The spring and fall experiments were carried on for 60 and 42 days, respectively. 7. Relationship between snail production and snail 39 biomass in laboratory streams. Enrichment of the streams with sucrose and urea produced heavy growths of Sphaerotilus natans. LIST OF' TABLES Table Page 1. Areas of the experimental sections of Berry Creek 7 in square meters. 2. Water quality summary for the Berry Creek experi- 10 mental stream during the Summer and Fall of 1962 and Winter and Spring, 19b3. 3. Average caloric values per gram dry weight of 18 experimental materials. 4. Comparison of mean snail weights taken from 24 growth curves with median weights obtained for the weight-frequency distributions of snails collected from Section III on August and November, 1964. Values are in milligrams dry weight. 5. Monthly growth rate, biomass, and production of 25 snails of the 1964 year-class. 6. Monthly growth rate, biomass, and production of 26 snails of the 1963 year-class. Annual production and annual mean biomass values are for the period March, 1964 through February, 1965.Total production and total mean biomass are for the 17-month period October, 1963 through Feburary, 1965. 7. Monthly growth rate, biomass, and production of 27 snails of the 1962 year-class. Annual production and annual mean biomass values are for the period March, 1963 through February, 1964.Total pro- duction arid total mean biomass are for the 17-month period October, 1962 through February, 1964. 8. Monthly growth rate, biomass, and production of 28 snails of the 1961 year-class. Annual production and annual mean biomass values are for the period March 1962 through February, 1963.Total pro- duction and total mean biomass are for the 17-month period October, 1961 through February, 1963. LIST OF TABLES (CONTINUED) Table Page 9. Monthly growth rate, biomass, and production of 29 snails of the 1960 year-class. Annual production and annual mean biomass values are for the period March, 1961 through February, 1962.Total pro- duction and total mean biomass are for the 17-month period October, 1960 through February, 1962. 10. Monthly growth rates, biomas s, and production of 30 the 1959 year-class. 11. Production by each year-class and total production 32 for unenriched Sections I and II and for enriched Sec- tions III and IV during the period March, 1964 through Februa ry, 1965.Values are in kilocalories per square meter. 12. Comparison of mean snail production values for the 34 unenriched sections and for the enriched sections be- tween the periods October, 1963 through February, 1964 and October, 1964 through February, 1965. Values are in kilocalories per square meter. 13. Estimated monthly food consumption in kilocalories 37 per square meter by all year-classes of snails in each experimental section for the year March, 1964 through February, 1965. 14. Rates of consumption by snails of alder, maple, and40 oak leaves (Experiment I July, 1964) and of alder and maple leaves (Experiment II August, 1964)sus- pended in packets in an unenriched section and inan enriched section of Berry Creek.Values are in milligrams dry weight of leaf pergram dry weight of snail per day. 15. Biomass in pounds per acre (flesh weight only) of 47 snails in Berry Creek compared with values deter- mined by other workers. Production of the Snail Oxytrema silicula (Gould) in an Experimental Stream INTRODUCTION Studies of the ways in which the energy from sunlight and allochthonous materials enters into the production of aquatic organ- isms have been underway at the Berry Creek experimental stream since 1959.An important part of these studies has been the investi- gation of the changes in the energy resources and production of cut- throat trout and other organisms that result from low-level enrich- ment of the stream with sucrose or with sucrose and urea.Enrich- ment, which began in 1960, has resulted in growths of the filamen- tous bacterium, Sphaerotilus natans, on the riffles of sections